add changelog entry

CHANGELOG.md

@@ -42,6 +42,7 @@
 - `[expect]` Move typings of `.not`, `.rejects` and `.resolves` modifiers outside of `Matchers` interface ([#12346](https://github.com/facebook/jest/pull/12346))
 - `[expect]` Throw useful error if `expect.extend` is called with invalid matchers ([#12488](https://github.com/facebook/jest/pull/12488))
 - `[expect]` Fix `iterableEquality` ignores other properties ([#8359](https://github.com/facebook/jest/pull/8359))
+- `[jest-circus, @jest/types]` Disallow undefined value in `TestContext` type ([#12507](https://github.com/facebook/jest/pull/12507))
 - `[jest-config]` Correctly detect CI environment and update snapshots accordingly ([#12378](https://github.com/facebook/jest/pull/12378))
 - `[jest-config]` Pass `moduleTypes` to `ts-node` to enforce CJS when transpiling ([#12397](https://github.com/facebook/jest/pull/12397))
 - `[jest-config, jest-haste-map]` Allow searching for tests in `node_modules` by exposing `retainAllFiles` ([#11084](https://github.com/facebook/jest/pull/11084))